Are you saving replays? Sounds like it from the save game sizes you mention.
Right now, I've been saving replays for
one patrol and my save folder is already over
2 gigs!!! Haven't got "Not Responding" yet on a reload but it takes increasingly longer to load the save game each time.
I may be wrong, but I think there is a "time-out" value set in the registry somewhere, if a program doesn't go "Hey, I'm still here!" within that time (in other words, it's busy reading files or crunching numbers and too busy to "check in" with Windows), Windows reports it as "Not Responding" even though it's still running fine. I've had many progs show as "Not Responding" while they're chewing on a CPU-intensive task but eventually they finish and all is well again
You might try waiting a little longer, and if you're saving replays you might want to stop and see if that helps any.
Good luck and don't give up! SH4
rules!
DH